Tsb Report: Aug 2008 B206l Crash Near Terrace

[Hello-bird]

Cap -

 

I remember being told about the emergency release... re: pickle the load. As well, I was told of the pilots options in such a situation, which you've clearly listed.

 

If a load does hit hard and the line does stretch this much with the pilot leaning out to this degree, would it not be quite difficult to control the machine/respond quickly appropriately re: emergency release(s) if the initial bounce was quite hard?

 

I also wonder if it would not be quite challenging to be smooth on the controls, as you say, in a situation where the machine might be considered underpowered for such a lift to begin with.

 

(Please forgive my questions if they are ignorant/obvious, because they are not obvious to me.)

 

HB

 

PS... Agreed. Mr. Yearwood is a great contribution to the field. And tends to go above and beyond the call of duty, so to speak, with regards not only to detailed investigation, but also in regards to compassionate (often hours & off the time clock) time spent with grieving family members of deceased. My hat's off to the man.

[splitpin]

Splitpin -----------Not a subject to introduce humour into, but sometimes it's needed to make a point. So just for you 'ol bean.

 

MCPHERSON SEATBELT ---- Begin construction by visiting your local Canadian Tire or trailer supply outlet. Purchase various sizes of ball hitches and the reason for doing so will become very apparent as you read on. You take these balls to your a/c and cut a hole through the padded seatcover at about the dead-center location. Once securely mounted, you now do a test run where a change of sizes may become necessary. The test run should be done by the most frequent user of that seat.

 

I know some Pilots that would require a "fifth-wheel mount" :up: :up: :up:

[Hello-bird]

I don't know a lot about it (first hand) but my understanding is that it occurs as a positive feedback loop between the pilot's hand and the collective and the airframe. That is, the airframe is oscillating up and down "around" the collective (airframe up, collective (relatively) down then vice versa). The vertical cycles quickly accelerate to the point of destruction - the blades flex into the tail boom (as in this case) or the tailboom breaks off. I've seen clips from a movie of the latter - only a few gyrations and everything comes apart.

 

It's initiated by a sudden vertical movement of the airframe while the collective/hand stays in place (vertically). This results in an unintended collective input opposite to the airframe travel which then reverses the cycle. Since the airframe - collective/hand form a positive resonant pair, things accelerate quickly.

 

I guess the stretchy longline would tend to induce bouncing in the airframe if the load hit the ground and the longline tried to contract. With lots of up-collective the line would stretch again and begin a vertical oscillation (?).

 

Although CAP explains that the phenomenon can be induced and corrected, my understanding is that it can become violent quite quickly.

 

The remedy is to dampen the free collective movement so that it will be more in phase with the vertical airframe movement, not out of phase with it. Apparently letting go of the collective will help, presumably it won't bounce up and down on it's own. Book value collective friction is the chosen safeguard.

 

I'm not certain of all my facts here - any one else is invited to correct.

 

Cheers . . . . .

 

Thank you for your explanation. It's easy to follow and gives a very clear picture. You explained it in the same way that it was explained to me in the hangar.

 

 

 

 

 

 

[rotrhd1]

Very informative discussion on collective bounce. Definitely something that should be included in everyones training.

 

I find it interesting throughout this thread that this has become the subject of discussion regarding this unfortunate incident. No mention of the fact the aircraft was 235 lbs over gross weight and 535 lbs over the HOGE chart "limit".

 

RH1

[dimit]

Good point, RH1.

 

On one hand, what's there to discuss? The facts speak for themselves...

 

On the other hand, for those who don't yet have the experience (or a good mentor) to convince them of the wisdom of flying within a/c limits, this is another reminder.

 

It's also a great example of how, in the course of a busy day, such an obvious thing as being a couple of hundred pounds over gross can slip past a very experienced and (presumably) wise pilot. It reminds me yet again of how vigilant we must be, and of how easy it is to get caught up in the job (or some distraction) and lose an important element of situational awareness.

 

Condolences to the family, friends, and colleagues of the pilot.

 

Dick

[cap]

Splitpin -------trucker talk eh? I know of quite a few, including myself one time, who couldn't get complete forward and aft cyclic travel either because of 'relaxed muscle' or a 'Molson muscle' hanging out over the pants buckle..........and that ball would've needed to be of some huge size to anchor all the resultant weight you see. Some even called me 'Baby Huey' and a few others I know of shared that name with me. It was all the result of the crowd I hung-out with, so it was all their fault.

 

 

 

 

HB---------in answer to your question(s).........NO!!. All checks about how far I can lean out before I'm in a position where I can't jetison my load in an emergency have already been done BEFORE committing to that hook-up for transport. I ain't waiting to find all that out during the emergency or AFTER, should I luckily survive that near-disaster. If I can't reach that emergency release in any fashion before T/O then a/c doesn't fly, engineer enters the picture to change same and/or I go for a 'cup 'o Joe' until it is changed. It's called the 'K.I.S.S. Principle'.

 

 

 

RH1-----------My subject of discussion was 'collective bounce' and NOTHING else was intended.........AND that was intentional. One can encounter same without being over gross weight OR past any HOGE limits. If someone may have surmised differently, then please take such an idea and flush it down the proverbial toilet ASAP.

[CJM91]

Good point, RH1.

 

On one hand, what's there to discuss? The facts speak for themselves...

 

On the other hand, for those who don't yet have the experience (or a good mentor) to convince them of the wisdom of flying within a/c limits, this is another reminder.

 

It's also a great example of how, in the course of a busy day, such an obvious thing as being a couple of hundred pounds over gross can slip past a very experienced and (presumably) wise pilot. It reminds me yet again of how vigilant we must be, and of how easy it is to get caught up in the job (or some distraction) and lose an important element of situational awareness.

 

Condolences to the family, friends, and colleagues of the pilot.

 

Dick

 

I too, wondered why this hadn't been mentioned sooner. To me this may be the larger issue - a manageable load likely would not have hit the deck with such force as to initiate the collective bounce.

 

I'm hard pressed to see how "a couple of hundred pounds over gross can slip past a very [especially] experienced and (presumably) wise pilot." However, drill crews have been known to slid the load off the deck into space, although they might not have tried this with the hydraulic pack.

 

However, I do agree with "It reminds me yet again of how vigilant we must be, and of how easy it is to get caught up in the job (or some distraction) and lose an important element of situational awareness." This could well include customer pressure to "go the extra mile". If this was the case, it turned out to be a very long mile.

 

I think that traditionally we have often tried too hard to please and for years have gone way too light on customer education as to operational limits and safety guidelines. We don't always have to say "Yes" but we do have to explain why, probably over and over again.

 

Cheers . . . .

[Heli500]

Thanks for the input on colective bounce. Up until this form I had never heard of it. Crazy what a little friction on the collective can prevent.

 

I just heard that Dart has gotten TC aproval to distribute the STC for McPherson Seatbelt seat modification kit. Applicable to all aircraft models.

 

Cheers

[Hello-bird]

HB---------in answer to your question(s).........NO!!. All checks about how far I can lean out before I'm in a position where I can't jetison my load in an emergency have already been done BEFORE committing to that hook-up for transport. I ain't waiting to find all that out during the emergency or AFTER, should I luckily survive that near-disaster. If I can't reach that emergency release in any fashion before T/O then a/c doesn't fly, engineer enters the picture to change same and/or I go for a 'cup 'o Joe' until it is changed. It's called the 'K.I.S.S. Principle'.

 

Got it (finally). Thanks.

HB

[212wrench]

Thanks for the input on colective bounce. Up until this form I had never heard of it. Crazy what a little friction on the collective can prevent.

 

Wow, I find that incredible. We teach AME student apprentices about collective bounce and min friction.